Biology subjects

Stier, G.

Publications and source records attributed to Stier, G..

3 recordsLinked to original sources

bioRxiv2021

DEAD-box RNA Helicases Act as Nucleotide Exchange Factors for Casein Kinase 2

DDX RNA helicases promote RNA processing but DDX3X is also known to activate casein kinase 1 {varepsilon} (CK1{varepsilon}). Here we show that not only is protein kinase stimulation a latent property of other DDX proteins towards CK1{varepsilon}, but that this extends to casein kinase 2 (CK22) as well. CK22 enzymatic activity is stimulated by a variety of DDX proteins and we identify DDX1/24/41/54 as physiological activators required for full kinase activity in vitro and in Xenopus embryos. Mutational analysis of DDX3X reveals that CK1 and CK2 kinase stimulation engages its RNA binding-but not catalytic motifs. Mathematical modelling of enzyme kinetics and stopped-flow spectroscopy converge that DDX proteins function as nucleotide exchange factor towards CK22 that reduce unproductive reaction intermediates and substrate inhibition. Our study reveals protein kinase stimulation by nucleotide exchange as a new principle in kinase regulation and an evolved function of DDX proteins.

biochemistry↗

bioRxiv2020

tructural basis for the complex DNA binding behavior of the plant stem cell regulator WUSCHEL

Stem cells are one of the foundational evolutionary novelties that allowed the independent emergence of multicellularity in the plant and animal lineages. In plants, the homeodomain (HD) transcription factor WUSCHEL (WUS) is essential for the maintenance of stem cells in the shoot apical meristem. WUS has been reported to bind to diverse DNA motifs and to act as transcriptional activator and repressor. However, the mechanisms underlying this remarkable behavior have remained unclear. Here, we quantitatively delineate WUS binding to three divergent DNA motifs and resolve the relevant structural underpinnings. We show that WUS exhibits a strong binding preference for TGAA repeat sequences, while retaining the ability to weakly bind to TAAT elements. This behavior is attributable the formation of dimers through interactions of specific residues in the HD that stabilize WUS DNA interaction. Our results provide a mechanistic basis for dissecting WUS dependent regulatory networks in plant stem cell control.

plant biology↗

bioRxiv2017

Signatures of the evolution of parthenogenesis and cryptobiosis in the genomes of panagrolaimid nematodes

Most animal species reproduce sexually, but parthenogenesis, asexual reproduction of various forms, has arisen repeatedly. Parthenogenetic lineages are usually short lived in evolution; though in some environments parthenogenesis may be advantageous, avoiding the cost of sex. Panagrolaimus nematodes have colonised environments ranging from arid deserts to arctic and antarctic biomes. Many are parthenogenetic, and most have cryptobiotic abilities, being able to survive repeated complete desiccation and freezing. It is not clear which genomic and molecular mechanisms led to the successful establishment of parthenogenesis and the evolution of cryptobiosis in animals in general. At the same time, model systems to study these traits in the laboratory are missing.\n\nWe compared the genomes and transcriptomes of parthenogenetic and sexual Panagrolaimus able to survive crybtobiosis, as well as a non-cryptobiotic Propanogrolaimus species, to identify systems that contribute to these striking abilities. The parthenogens are most probably tripoids originating from hybridisation (allopolyploids). We identified genomic singularities like expansion of gene families, and selection on genes that could be linked to the adaptation to cryptobiosis. All Panagrolaimus have acquired genes through horizontal transfer, some of which are likely to contribute to cryptobiosis. Many genes acting in C. elegans reproduction and development were absent in distant nematode species (including the Panagrolaimids), suggesting molecular pathways cannot directly be transferred from the model system.\n\nThe easily cultured Panagrolaimus nematodes offer a system to study developmental diversity in Nematoda, the molecular evolution of parthenogens, the effects of triploidy on genomes stability, and the origin and biology of cryptobiosis.

evolutionary biology↗